FIG. 7 is a figure showing a structure of a conventional woven fabric for the loud-speaker diaphragms. A woven fabric 10 used for the diaphragm of the loud-speaker comprises threads 11 and 12 made of a single material. Although in a certain case these threads 11 and 12 may be made of a material of one kind, in some cases a fabric may be woven using two or more kinds of materials as shown in FIG. 7. As a variation of a method for manufacturing the woven fabric 10 for the loud-speaker diaphragms, the woven fabric is obtained by weaving threads 11 and 12 of different kind. As a material of the threads 11 and 12, glass, polyester or polypropylene is usually used.
The woven fabric is wholly colored with pigments or dyestuffs in a coloring process of the woven fabric 10 for the loud-speaker diaphragm manufactured by using fibers of the threads 11 and 12 of different kind. Moreover, in the case where the threads 11 constituting the woven fabric 10 for the loud-speaker diaphragm are already colored threads 11 (a glass fiber, a polyester fiber or a polypropylene fiber), the resulting woven fabric is not further colored, but the original color of the threads 11 is represented as a color of the woven fabric 10.
In addition, PBO (poly(p-phenylene benzobisoxazole)) fiber is sometimes employed for threads 12 and interwoven with a glass fiber, a polyester fiber 11 or a polypropylene fiber in order to increase a strength of the woven fabric 10 covering a surface. In this case, several threads 11 and 12 are alternately interwoven into this fabric as shown in FIG. 7.
When two or more kinds of threads 11 and 12 are interwoven into plain fabric to obtain the conventional woven fabric 10 for the loud-speaker diaphragm, because, for example, the threads 11 and 12 may not be dyed into the same color, sometimes the resultant colors of the threads 11 and 12 may be different from each other. There is caused problem that the appearance is adversely affected by a lattice pattern formed in the woven fabric 10 for the loud-speaker diaphragm because of the above described different coloring. On the other hand, in the case where original color of the threads 11 and 12 of different kind is represented without carrying out any dyeing treatment, although omission of dyeing process is advantageous, the resultant lattice pattern appears to be more remarkable.
It is preferable that the woven fabric is colored after the woven fabric 10 is woven so that a lattice pattern will not appear in the color of the woven fabric 10 for the loud-speaker diaphragm. However, since this woven fabric 10 is used for the surface of the diaphragm of the loud-speaker, it is required that the woven fabric 10 itself has a tensile strength higher than a specific value. Therefore it is desirable to employ a PBO material that has the high tensile strength and enough durability against vibration of the loud-speaker.
However, when the PBO fiber is woven into the fabric, the above described problem of formation of the lattice pattern becomes more noticeable. The PBO fiber has a characteristic that the PBO fiber itself is difficult to be colored and has originally golden color that gradually changes into amber by being exposed to light. For this reason, in a coloring process, only a method of adding pigments having a color deeper than original color of the PBO fiber is employable. When this colored PBO fiber is interwoven into woven fabric together with other fibers (a glass fiber, a polyester fiber or a polypropylene fiber), it may provide in a finished fabric a clear lattice pattern because each fibers are colored to the different extent.
The present invention provides a solution for the above described problem. Therefore the object of the present invention is to provide the woven fabric for the loud-speaker diaphragm with increased tensile strength in which no lattice pattern is formed even with use of plural and different kinds of fibers, and to provide the loud-speaker diaphragm using the woven fabric and the loud-speaker having the diaphragm covered with the woven fabric.